The possibilities offered by micromechanics 'below macro' are entering all fields of application, ranging from traditional solid materials to multiphase material systems in geomechanics and biomechanics. The 13 papers in this special issue on micromechanics of porous materials focus on advances in methods and applications. Topics include: Continuum Micromechanics; Upscaling Heterogeneous Media by Asymptotic Expansions; Mechanics of Composite Solids; Local Geometry and Transports of Real Porous Media; Extension of Poroelastic Analysis to Double-Porosity Materials; Micromechanical Approach to Nonlinear Poroelasticity - Application to Cracked Rocks; Micromechanics of Unsaturated Granular Media; Micromechanical Basis of Concept of Effective Stress; Failure Properties of Fractured Rock Masses as Anisotropic Homogenized Media; Effects of Inclusions on Friction Coefficient of Highly Filled Composite Materials; Homogenized Behavior Equations for Porous Bingham Viscoplastic Material; Micromechanical Analysis of Anisotropic Damage in Brittle Materials; and Micromechanical Model for Ultrastructural Stiffness of Mineralized Tissues.